Cross brace for a platform assembly



FIG. 1 is a left front perspective view of a cross brace for a platform assembly showing my new design;

FIG. 2 is a front elevational view, the rear being a mirror image thereof;

FIG. 3 is a right end elevational view, the left end being a mirror image thereof; and

FIG. 4 is a top plan view, the bottom being a mirror image thereof. 

The ornamental design for a cross brace for a platform assembly, as shown and described. 